1. Field of the Invention
The present invention is related to making and using an injection-molding nozzle incorporating, a removable heating device and a heating device clamping mechanism associated therewith.
2. Background Art
Typically, injection-molding nozzles have a nozzle body including a melt channel with a heater element proximate thereto. Heaters in injection nozzles ideally produce a constant or consistent viscosity and speed of a melt stream of moldable material, which produces accurate items that are uniform in appearance. In conventional injection molding systems, when a heater starts to improperly function or fails completely, the entire nozzle might need to be removed from a manifold connection and replaced. Removing and replacing a nozzle requires shutting down a production line for an extended period of time. This increases manufacturing costs because of the expense of having to replace an entire nozzle, the inefficiency of production time, and the cost for labor being idle during removal and replacement of a nozzle.
A first type of heater element can be a “wrap around clamp” heater, such as a tubular heater, film heater, band heater, or a helical coil heater. The wrap around clamp heaters are wrapped around the nozzle body to uniformly heat the melt channel. If these wrap around heaters fail to perform while in operation, an operator must a) remove the heater by sliding it over the nozzle and towards the nozzle tip from the mold side, if there is access from the mold side, or b) remove the entire nozzle if there is no access from the front of the nozzle. Clamp heaters for hot runner nozzles are known, such as those disclosed in U.S. Pat. No. 5,411,392 to Von Buren, U.S. Pat. No. 6,409,497 to Wurstlin, U.S. Pat. No. 5,360,333 to Schmidt, U.S. Pat. No. 6,043,466 to Jenko et al, and U.S. Pat. No. 4,268,241 to Rees et al, which are all incorporated herein by reference in their entireties.
Most of the clamp heaters for hot runner application use a heater element attached to a cylindrical heater sleeve that incorporates a clamping mechanism. The clamping mechanism of the heater makes sure that an intimate contact is created between the heater sleeve and the nozzle body to provide maximum heat transfer and heat efficiency. In most cases either the heater element or the heater sleeve have a longitudinal or an axial cut or a disruption to allow the heater or the sleeve to be squeezed towards the nozzle body under the clamping force.
Another type of heater element is an embedded heater, such as a cast-in heater, cartridge heater, pressed in heater and heat pipe heater, which are located entirely inside (embedded in) the nozzle body proximate to and/or surrounding a melt channel. These embedded heaters tend to provide a desirable heat profile, a desirable heat transfer, and a desirable heat efficiency because they are located in intimate contact within the nozzle body. Embedded heaters tend to be disposed closer to the melt channel than the wrap around removable heaters. However, when the embedded heaters improperly function or fail, an entire nozzle must be replaced.
A third type of heater is related to the flat injection molding nozzles heater, such as cartridge heaters, where the heater is located inside the nozzle and/or coupled to the nozzle on one or two (possibly opposite) sides of the melt channel, usually inside the nozzle body. These heaters are typically used with flat small pitch nozzles and are in most instances located on a single side or opposite sides of the melt channel. These heaters can be clustered into arrays of two or more nozzles and are utilized in areas with very limited space.
For example, German patent application DE 19723374 assigned to Heitec teaches a flat nozzle for small pitch applications having one or two cylindrical cartridge heaters. The Heitec heaters are totally embedded inside the nozzle body, which prevents the heaters from receiving maintenance without removing the nozzles from the system. Another example is U.S. Pat. No. 6,619,948 to Gunther that shows a nozzle surrounded by a flat case. The flat case includes one or two embedded cylindrical heater elements. However, the Gunther heaters cannot be removed from the case while keeping the case fully installed on the nozzle. Thus, production must be completely shutdown so that a clearance space can be created between the nozzle and the mold for the removal of the case. Both of the above references are incorporated herein by reference in their entireties.
Some examples of other embedded heaters for injection molding nozzles can be found in U.S. Pat. Nos. 4,882,469, 4,899,435, 4,906,360, 4,988,848, 5,052,100, 5,055,028, 5,098,280, 5,136,141, 5,147,663, 5,180,594, all to Trakas, which are all incorporated herein by reference in their entireties.
Therefore, what is needed is a system and method to remove a faulty heater embedded in an injection nozzle, while allowing the nozzle to remain in contact with a manifold. What is also needed is a nozzle that allows for only a heater to be removed and replaced in a relatively short amount of time without requiring shutting down of operations and removal of the entire nozzle. What is also needed is an injection nozzle where a removable heater has an improved clamping function to increase heat transfer efficiency.